Latex polymers are useful in the production of several products, including binders for filler particles in paper coating, carpet backing, paints, foams, and adhesives. The mechanical properties of these products can be improved through the addition of inorganic materials to the dispersions or resultant products. Typically, these inorganic materials are added to the dispersion prior to being used in the resultant products. Although there have been attempts to add the inorganic material during the polymerization reaction to form a dispersion consisting of polymer-inorganic hybrid particles, these processes have also required difficult and time consuming treatment processes to use the inorganic material during the polymerization process.
For example, clay-rubber nanocomposites have been developed by various methods, including in-situ solution polymerization and co-coagulating a rubber latex and a clay aqueous dispersion. In the solution polymerization process, the polymer is dissolved into an organic solvent, i.e. toluene. Separately, a clay that has been modified to be organophilic is dispersed in another organic solvent, i.e. alcohol. A desired amount of the clay dispersion is poured into the polymer solution under agitation. The solution is then dried under vacuum to remove the organic solvent to prepare the polymer/clay composite.
In the co-coagulation method, a modified organophilic clay is dispersed in water and added into the polymer dispersion (latex). After vigorous stirring, the mixture is co-coagulated by addition of the electrolyte solution (i.e. 2% sulfuric acid solution). The resultant coagulum is washed with water and dried.
In these processes, the clay surface needs to be pretreated to be organophilic so the clay particles dispersed into the aqueous phase of the polymer dispersion can be incorporated into the bulk polymer phase to produce the clay/rubber polymer nanocomposite. One drawback of these processes is that natural, hydrophilic clay particles cannot be used. For example, in the co-coagulation process, the natural, hydrophilic clay particles would simply coagulate by themselves and form macroscopic separate phases during the coagulation process. Furthermore, these processes produce dry rubber solids which limit the industrial applications where these nanocomposites can be used. These solids are especially difficult to use in adhesives, foams, asphalt emulsions, and other applications.